linux-kernel - [PATCH] vsprintf: Add test for restricted kernel pointers

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Message-Id: <20260114-restricted-pointers-kunit-test-v1-1-a9d8a49c6b6f@linutronix.de>
Date: Wed, 14 Jan 2026 08:27:34 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, 
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
 Rasmus Villemoes <linux@...musvillemoes.dk>, 
 Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH] vsprintf: Add test for restricted kernel pointers

Fill out the tests for restricted kernel pointers, using the %pK format.
This test can only be executed when built into the kernel, as modules
do not have access to the kptr_restrict knob.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
---
Please note that changes to the kptr_restrict sysctl from the kernel
commandline are only applied *after* the boot-time KUnit tests run.
---
 lib/tests/printf_kunit.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/lib/tests/printf_kunit.c b/lib/tests/printf_kunit.c
index 7617e5b8b02c..af15d2ab4046 100644
--- a/lib/tests/printf_kunit.c
+++ b/lib/tests/printf_kunit.c
@@ -316,7 +316,31 @@ symbol_ptr(struct kunit *kunittest)
 static void
 kernel_ptr(struct kunit *kunittest)
 {
-	/* We can't test this without access to kptr_restrict. */
+#ifdef MODULE
+	kunit_skip(kunittest, "cannot access kptr_restrict from test module");
+	return;
+#endif
+
+	switch (kptr_restrict) {
+	case 0:
+		if (no_hash_pointers) {
+			test(PTR_STR, "%pK", PTR);
+		} else {
+			char buf[PLAIN_BUF_SIZE];
+
+			plain_hash_to_buffer(kunittest, PTR, buf, PLAIN_BUF_SIZE);
+			/* %pK behaves the same as hashing */
+			test(buf, "%pK", PTR);
+		}
+		break;
+	case 1:
+		test(PTR_STR, "%pK", PTR);
+		break;
+	case 2:
+	default:
+		test(ZEROS "00000000", "%pK", PTR);
+		break;
+	}
 }
 
 static void

---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20260109-restricted-pointers-kunit-test-ff4ec887bcd8

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@...utronix.de>